Convection heat exchanger

ABSTRACT

A convection heat exchanger in which the fins of a fin-and-tube assembly each have U-shaped, spaced-apart edges which define a fin surface of a given area confined between lateral boundaries spaced-apart a distance smaller than the developed length of either edge.

-shaped, spaced- United States Patent [1 1 1 Wenig [451 CONVECTION HEATEXCHANGER Prima Examiner-Charles J. M hre 76ItzN B.Wl39I-Ik Y 1 men or zl f er [met Assistant Examiner-Theophil W. Streule, Jr.

Attorney-Irving Seidman et al. [22] Filed: Jan. 3, 1972 [21] Appl. No.:214,760

. [57] ABSTRACT [52] [1.5. 165/55, 165/18! 5 [51] Int. F281 1/10 Aconvection heat h ng r in hi h the fins of a [58] Field ofSearch........................ 165/55, 56, 187 fin-and-tube assemblyeach have U apart edges which define a fin surface of a given area [56]Refer n e Cit d confined between lateral boundaries spaced-apart aUNITED STATES PATENTS distance smaller than the developed length ofeither 3,367,132 2/1968 165/55 x edge FOREIGN PATENTS OR APPLICATIONS 2Claims 4 Drawing Figures 507,927 9/1930Germany............................ 165/181 CONVECTION HEAT EXCHANGERBACKGROUND AND SUMMARY OF THE INVENTION This invention relates ingeneral to fin-and-tube type heat exchangers, and more particularly to afin-andtube assembly in which the fins have a special configuration thatgives a more compact assembly for a given output rating.

In the prior art, fin-and-tube assemblies used in con vection radiatorshad a plurality of heat exchanger tubes extending through a multiplicityof rectangular fins. These heat exchanger tubes were ordinarilyparallel, located in a common plane elevated above the floor about seveninches. All tubes of the same assembly were manifold connected at eachend, and plumbing connections to the manifolds were by pipes extended upthrough the floor.

The typical radiator unit has an enclosure which defined an air fiowpath from an inlet opening at the bottomto an outlet grill at the top.The fin-and-tube assembly within the enclosure was located as close tothe bottom as permitted by the standard plumbing connections so as tomaximize the natural draft effect obtainable with a given height ofenclosure. This draft or chimney effect is determined by the differencein elevation between the fin-and-tube assembly and the hot air outlet,and inany case it is advantageous to increase the draft because theresultant increase in air flow past the fin-andtube assembly givesbetter heat transfer with natural convection. Thus, for a givenfin-and-tube assembly, a higher BTU heat output rating can be achievedby making the draft as high as possible.

In modern buildings, it is desirable in many cases to have radiatorunits that can be recessed flush into standard sized walls. Accordingly,it is advantageous to be able to make the fin-and-tube assemblies forsuch radiators as compact as possible, particularly in their depthdimensions.

The invention provides a fin-and-tube heat exchanger assembly for aconvection type radiator that improves the overall heat transfercapability to the extent that a radiator unit of a given thermalcapacity can be made more compactthan would be possible using prior artdesigns.

In the heat exchanger design of the invention, the fins of thefimand-tube assembly each have U-shaped, spaced-apart edges which definea fin surface of a given area confined between lateral boundariesspaced-apart by a distance that is smaller than the developed length ofeither side. This allows the fin-and-tube assembly to be made smallerboth depthwise and lengthwise than would be possible using prior artrectangular fins.

According to one embodiment of the invention, the spacing and contour ofthese U-shaped edges are such that the fins are of crescent-shapedconfiguration, and according to another embodiment, the fins are more ofa U-shaped configuration with rectangular corners. By using such finconfigurations, more heat transfer surface is placed closer to the inletof the radiator enclosure for greater natural draft than would beachieved for the same tubes carrying rectangular fins. Consequently,such improved heat transfer allows economical reductions in the numberand size of the tubes.

While the invention basicly contemplates fins with U-shaped edges, theartisan will appreciate an exact U- shape is not essential and the edgescan even be approximately V-shaped.

With the invention, the cabinet enclosure and fin and-tube assembly canbe made smaller for a given BTUI-I rating. Conversely, the same cabinetand finand-tube assembly gives a higher BT UH rating than in the priorart.

For a better understanding of the invention and its several advantages,reference should be had to the accompanying drawing and following,detailed description pertaining to certain preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective view, partly broken away, of a convectionradiator equipped with a fin-and-tube heat exchange assembly constructedin accordance with a preferred embodiment of the invention.

FIG. 2 is a perspective view of the fin-and-tube as sembly shown in FIG.1 as seen removed from the radiator enclosure.

FIG. 3 is a view of a typical fin used in the fin-andtube assembly ofFIG. 2.

FIG. 4 is a view of a different fin configuration that can besubstituted for that shown in FIG. 3 to make a fin-and-tube assembly inaccordance with another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1there is shown a convection radiator I0 having an enclosure 11 withinwhich is situated a finand-tube heat exchanger assembly 12, shownseparately in FIG. 2.

Enclosure l1 defines an air flow path that extends from inlet opening I3adjacent the floor 14, up past assembly 12 to outlet grill 15 at the topof enclosure 11.

Assembly 12 has a plurality of laterally spaced-apart heatexchangertubes 16 disposed generally parallel at the same elevationplane above floor 14. At opposite ends, tubes 16 are connected tomanifolds 17 which in turn are connected to pipes 18 that extend upthrough floor 14. To allow reasonable working space for making up theplumbing connections, pipes 18 are extended about seven inches abovefloor I4, and according to standard practice in the art, the connectionsof pipes 18 to manifolds 17 are made no lower than such height.

On tubes 16 are carried a multiplicity of transversely disposed fins 19,shown in detail by FIG. 3. To protect the fins 19 from handlingdamage,assembly 12 is laterally enclosed by a rectangular frame 20.

From FIG. 3 it can be noted that the fins 19 are crescent-shaped and inaddition to holes 21 for insertion of tubes 16, each fin 19 has a pairof U-shaped edges 22 and 23 that-are disposed in spaced-apart relationto define a fin 19 surface of a given area confined between lateralboundaries WI and W2 spaced apart a distance smaller than the developedlength of either one of the edges 22, 23.

Fin edges 22 and 23 are preferably located symmetrically with respect tothe heat exchanger tubes 16, and the holes 21 are therefore placedequidistantly from the central line of symmetry W0.

Edges 22 and 23 are expediently circular arcs of the same radius R butwith centers spaced-apart on line W0 by a distance h. Consequently, theedges 22 and 23 will be uniformly spaced apart by the distance h asmeasured parallel to line W0. This type of fin configuration isadvantageous because it allows more heat transfer surface to be carriedbetween lateral boundaries W1 and W2 than would be possible withrectangular fins (not shown) equal in width to the distance between W1and W2, and equal in height to h. Furthermore, such configuration placesa certain amount of heat transfer surface below the tubes 16, so that ina given size enclosure 11, greater output is obtained as compared to thesame tubes 16 with rectangular fins, because of the increase ineffective draft height, with the same total fin area.

in FIG. 4 there is shown a fin 25 having a somewhat differentconfiguration and which can be substituted for the fin 19 in themanufacture of an assembly 12. Pin 25 has holes 26 located and sized forinsertion of tubes 16, and a pair of U-shaped edges 27 and 28 that areuniformly spaced-apart as measured parallel to the central line ofsymmetry. Within given lateral boundaries the fin 25 can presentsomewhat more surface than the fin l9 configuration, because therectangular corners 29 and 30 add area that would be lost if the edge 28were to be cut along the arcuate continuation lines 31 (shown inphantom).

It should be noted that the fins 19, 25 are placed upon tubes 16 so thatthe convex edges 23, 28 respectively are oriented toward the inlet sideof the air flow, in order to maximize the induced draft by placing theeffective heating surface further from the outlet grill 15.

The invention is readily adapted to meet the needs of a specificapplication, as will become obvious to the artisan from the descriptionherein of a limited number of preferred embodiments of the invention.

What is claimed is:

l. A convection heat exchanger which comprises an enclosure adapted torest upon an underlying base surface and having an inlet adjacent suchbase surface and an outlet at an elevation thereabove, said enclosuredefining an airflow path extending from said inlet to said outlet, aplurality of laterally spaced-apart heat exchanger tubes disposed withinsaid enclosure at an intermediate elevation above such base surface, anda multiplicity of transversely disposed similar fins carried by saidtubes in symmetrically disposed relation thereto, said fins each havinga pair of U-shaped, curved edges disposed in vertically spaced-apartrelation to define a fin surface of a given area confined betweenlateral boundaries spaced-apart a distance smaller than the developedlength of one of said edges.

2. A convection heat exchanger according to claim 1 wherein said finshave rectangular corners positioned in alignment with one another.

1. A convection heat exchanger which comprises an enclosure adapted torest upon an underlying base surface and having an inlet adjacent suchbase surface and an outlet at an elevation thereabove, said enclosuredefining an airflow path extending from said inlet to said outlet, aplurality of laterally spacedapart heat exchanger tubes disposed withinsaid enclosure at an intermediate elevation above such base surface, anda multiplicity of transversely disposed similar fins carried by saidtubes in symmetrically disposed relation thereto, said fins each havinga pair of U-shaped, curved edges disposed in vertically spaced-apartrelation to define a fin surface of a given area confined betweenlateral boundaries spaced-apart a distance smaller than the developedlength of one of said edges.
 2. A convection heat exchanger according toclaim 1 wherein said fins have rectangular corners positioned inalignment with one another.